Recent results from the Epidemiological Catchment Area (ECA) program suggest that the prevalence rates of psychiatric disorder (lifetime and recent) for the elderly are considerable lower than those for other age groups. In this proposal we hypothesize that these results could be biased, at least in part, by methodological procedures involved in the probe sequence of the Diagnostic Interview Schedule (DIS)--a series of probe questions used to ascertain the clinical significance of a respondent's symptomatology. Three factors may be at work. First is that the elderly are likely to experience more age-related impairments in cognitive functioning and subsequently have more problems recalling past symptomatology (the Differential-Recall Hypothesis). This operates to generate false negatives among the elderly. Second, the elderly are more likely than younger age groups to seek help from the general medical sector. Given the nature of the DIS's probe sequence, it is hypothesized that this may result in false negatives among the elderly and false positives among the young (the Service-Exposure Hypothesis). Third, it is hypothesized that the probe procedure for assessing the significance of a symptom, in the absence of a doctor's evaluation, is affected by age-related styles in attributing causes for symptoms, with the elderly more likely than the young to attribute symptoms to medical causes (the Attributional-Styles Hypothesis). The general objective of this research is to examine the tenability of each of these hypotheses using data from the Colorado Social Health Survey in combination with parallel data from the Duke Epidemiologic Catchment Area Study. Both studies employed the DIS.